1. Field
The invention relates to retaining a treatment agent at a treatment site with a bioerodable gel.
2. Relevant Art
A major component of morbidity and mortality attributable to cardiovascular disease occurs as a consequence of the partial or complete blockage of vessels carrying blood in the coronary and/or peripheral vasculature. When such vessels are partially occluded, lack of blood flow causes ischemia to the muscle tissues supplied by such vessel, consequently inhibiting muscle contraction and proper function. Total occlusion of blood flow causes necrosis of the muscle tissue.
Blood vessel occlusions are commonly treated by mechanically enhancing blood flow in the affected vessels. Such mechanical enhancements are often provided by employing surgical techniques that attach natural or synthetic conduits proximal and distal to the areas of occlusion, thereby providing bypass grafts, or revascularization by various means to physically enlarge the vascular lumen at the site of occlusion. These revascularization procedures involve such devices as balloons, endovascular knives (atherectomy), and endovascular drills. The surgical approach is accompanied by significant morbidity and even mortality, while the angioplasty-type processes are complicated by recurrent stenoses in many cases.
In some individuals, blood vessel occlusion is partially compensated by natural processes, in which new vessels are formed (termed “angiogenesis”) and small vessels are enlarged (termed “arteriogenesis”) to replace the function of the impaired vessels. These new conduits may facilitate restoration of blood flow to the deprived tissue, thereby constituting “natural bypasses” around the occluded vessels. However, some individuals are unable to generate sufficient collateral vessels to adequately compensate for the diminished blood flow caused by cardiovascular disease. Accordingly, it would be desirable to provide a method and apparatus for delivering agents to help stimulate the natural process of therapeutic angiogenesis to compensate for blood loss due to an occlusion in a coronary and peripheral arteries in order to treat ischemia.
In some therapies, e.g., cardiovascular-related, cancer-related, and certain surgical or minimally-invasive therapies, it may be desirable to inject a treatment agent of or including a sustained release matrix intralumenally, intracardially, or intraventricularly. Unfortunately, however, it is generally difficult to retain the treatment agent at a desired treatment site. In cardiovascular-related therapies, for example, rarely is greater than 30 percent of the sustained release matrix retained at the injection site following such therapies. The loss of sustained release matrix generally occurs either during the initial injection or as a result of backflow from the needle site. The backflow from the needle site can occur due to an excessive amount of fluid required to deliver the matrix material, or, as the needle is removed from the injection site, the site does not seal before matrix material escapes. The consequences of matrix material escaping can be multifold depending on the interaction of the matrix and the surrounding blood or fluid.
The loss of matrix material and release can result in inconsistent dosage delivery. The inconsistency in dosage delivery in turn results in the delivery of the treatment agent that possibly will be at a dosage outside of the desired or optimum therapeutic window. In the case of arterial or ventricular treatment sites, a second response would occur if the sustained release matrix has thrombogenic effects, resulting in the formation of thrombosis that may have severe consequences in the arterial or ventricular region.
What is needed is a technique for retaining a treatment agent, including a treatment agent of or including a sustained-release matrix at a treatment site.